Government legislated fuel economy and pollution standards have resulted in efforts by both automotive companies and additive suppliers to enhance the fuel economy of motor vehicles. An additional pressure requiring enhanced fuel economy is the ever rising cost of fuel.
It is well-known that the performance of gasoline and other fuels can be improved through the use of additives. For example, detergents can be added to inhibit the formation of intake system deposits, thereby improving engine cleanliness. More recently, friction modifiers have been added to gasoline to increase fuel economy by reducing engine friction. In selecting suitable components for a detergent or friction modifier additive, it is important to ensure a balance of properties. For example, the friction modifier should not adversely affect the deposit control of the detergent. In addition, the additive package should not exhibit any harmful effects on the performance of the engine, such as valve sticking.
One approach to achieving enhanced fuel economy is to improve the efficiency of the engine in which the fuel is used. Improvement in engine efficiency can be achieved through a number of methods, e.g., improved control over fuel/air ratio, decreased crankcase oil viscosity, and reduced internal friction at specific, strategic areas of an engine.
With respect to reducing friction inside an engine, about 18% of the heat value of fuel is dissipated through internal friction (e.g., bearings, valve train, pistons, rings, water and oil pumps), whereas only about 25% is actually converted to useful work at the crankshaft. The piston rings and part of the valve train account for over 50% of the friction and operate at least part of the time in the boundary lubrication mode during which a friction modifier may be effective. If a friction modifier reduces friction of these components by a third, the friction reduction corresponds to about a 35% improvement in the use of the heat of combustion and is reflected in a corresponding fuel economy improvement. Therefore, investigators continually search for fuel additives that reduce friction at strategic areas of the engine, thereby improving the fuel economy of engines.
Lubricating oil compositions also contain a wide range of additives including those which possess anti-wear properties, anti-friction properties, anti-oxidant properties, and the like. Those skilled in the art of designing lubricating oils therefore are continuously seeking additives that can improve these properties, without a detrimental effect on other desired properties.
Over the years considerable work has been devoted to designing additives that reduce friction in internal combustion engines. For example, U.S. Pat. Nos. 2,252,889, 4,185,594, 4,208,190, 4,204,481, and 4,428,182 disclose additives for diesel engine fuels consisting of fatty acid esters, unsaturated dimerized fatty acids, primary aliphatic amines, fatty acid amides of diethanolamine, and long-chain aliphatic monocarboxylic acids.
U.S. Pat. No. 4,427,562 discloses a friction reducing additive for lubricants and fuels formed by the reaction of primary alkoxyalkylamines with carboxylic acids or alternatively by the ammonolysis of the appropriate formate ester.
U.S. Pat. No. 4,729,769 discloses a detergent additive for gasoline, which contains the reaction product of a C6-C20 fatty acid ester, such as coconut oil, and a mono- or di-hydroxyalkylamine, such as diethanolamine or dimethylaminopropylamine.
Other patents disclosing alkanolamides and alkoxylated alkanolamides useful as fuel additives include U.S. Pat. Nos. 4,446,038; 4,512,903; 4,525,288; 4,647,389; 4,765,918; 6,743,266; 6,589,302; 6,524,353; 4,419,255; 6,277,158; 4,737,160; U.S. Pat. Publication No. 2003/0056431; U.S. Pat. Publication No. 2004/0154218; U.S. Pat. Nos. 6,786,939; 6,689,908; U.S. Pat. Publication No. 2006/0047141; U.S. Pat. Nos. 6,034,257; 6,534,464; U.S. Pat. Publication No. 2005/0026805; U.S. Pat. Publication No. 2005/0233929; U.S. Pat. Publication No. 2003/0091667; U.S. Pat. Publication No. 2005/0053681; U.S. Pat. Nos. 6,764,989; 5,979,479; 5,339,855; WO 2005/113694; U.S. Pat. No. 6,746,988; U.S. Pat. Publication No. 2004/0231233; U.S. Pat. No. 6,531,443; WO 99/46356; U.S. Pat. Nos. 6,277,191; and 5,229,033.
However, a need still exists for an improved additive for gasoline and other hydrocarbon-based fuels that provides sufficient friction reduction to enhance fuel economy, that is stable over the temperature range at which the additive is stored, and that does not adversely affect the performance and properties of the finished gasoline or an engine in which the gasoline is used.